Wojciech Szczęsny knew what he was getting into at Juventus. When he signed from Roma in the summer of 2017, he gave up a starting role to serve as understudy to Gianluigi Buffon. There were no guarantees for what would happen after his first season in Turin.

“I came here hoping that I would become the starter of the future, but I need to earn it,” he told La Repubblica last December. He had been with the club for five months, and played a handful of games, yet to his mind it was clear that “what I am today is still not enough. A team like Juventus needs to have one of the best keepers in the world.”

That final sentiment was echoed by Owen Hargreaves this month, in a rather less optimistic tone. The former England midfielder was serving as a pundit for British broadcaster BT Sport on its coverage of Juventus’ Champions League defeat at home to Manchester United.

Szczęsny had been at fault on the game’s winning goal, hesitating as a cross came...